Ultrasonic instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate organic tissue using energy in the form of mechanical vibrations transmitted to a surgical end-effector at ultrasonic frequencies. Ultrasonic vibrations, when transmitted to organic tissue at suitable energy levels and using a suitable end-effector, may be used to cut, dissect, or cauterize tissue. Ultrasonic instruments utilizing solid core technology are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from the ultrasonic transducer, through the waveguide, to the surgical end-effector. Such instruments may be used for open procedures or minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end-effector is passed through a trocar to reach the surgical site.
Activating the end-effector (e.g., cutting blade) of such instruments at ultrasonic frequencies induces longitudinal vibratory movement that generates localized heat within adjacent tissue, facilitating both cutting and coagulation. Because of the nature of ultrasonic instruments, a particular ultrasonically actuated end-effector may be designed to perform numerous functions, including, for example, cutting and coagulation. The structural stress induced in such end-effectors by vibrating the blade at ultrasonic frequencies may have a number of undesirable effects. Such undesirable effects may include, for example, transverse motion in the instrument waveguide that may lead to, for example, excess heat generation in the waveguide or premature stress failure.
Although ultrasonic surgical instruments have been eminently successful, some areas of improvement still remain. For example, it would be desirable for improved ultrasonic blades to remove the gall bladder from the liver bed and for coagulation to facilitate the procedure. An ultrasonic blade that enables efficient dissection of the gall bladder from the liver bed using proximal and distal surfaces facilitates the surgical technique. An ultrasonic blade which has a hook or right angle or near right angle bend near the distal end would provide advantages for access and visibility. The challenges to providing such a configuration have been stress and balance related. An ultrasonic blade with such a configuration must be behave in a balanced manner and be sufficiently strong to endure the added stresses. It would, therefore, be desirable to design an improved ultrasonic surgical blade. It would further be advantageous to provide an ultrasonic surgical blade that cuts faster, while maintaining hemostasis desired by the surgeon. It would also be advantageous to provide an ultrasonic surgical blade that is more controllable and precise, to providing cutting where needed with significant control. An ultrasonic surgical instrument is described with improved cutting and coagulation features to provide these advantages and overcome the disadvantages of previous instruments.